1. Introduction
The choice of animal models is crucial in physiology, cellular biology, and related disciplines. A particularly intriguing model is the rodent genus
Acomys, or spiny mouse (specifically
Acomys cahirinus), known for its advanced regenerative capabilities, which have been extensively studied in the context of skin and muscle regeneration [
1,
2,
3,
4].
Acomys is a precocial animal. At birth, its eyes are fully open, and the animal can engage in visually guided locomotion [
5]. However, limited data are available on the structure and postnatal development of the visual system in
A. cahirinus [
6]. This paper is the first in a series of publications to explore the structure and postnatal development of the central nervous system and the visual in particular, in
A. cahirinus. Our first objective was to examine the main visual thalamic structure, the lateral geniculate nucleus (LGN), in adult and newborn
A. cahirinus. In this study, we used several neurochemical markers to visualize distinct populations of interneurons and relay neurons, including Ca
2+-binding proteins, the enzyme glutamic acid decarboxylase isoform with 67 kDa molecular weight (GAD67), and non-phosphorylated domains of high-weighted neurofilaments. In the LGN, Ca
2+-binding proteins such as calbindin (CB), calretinin (CR), and parvalbumin (PV) are predominantly expressed in local populations of interneurons across rodents [
7,
8], carnivores [
9,
10], and primates [
11,
12]. The enzyme GAD67 catalyzes GABA synthesis and is found in inhibitory interneurons [
13,
14]. The non-phosphorylated domains of the high-weighted neurofilaments labeled by SMI-32 antibodies [
15] in rodents, carnivores, and primates are predominantly expressed in the large relay geniculate neurons [
7,
16,
17]. In carnivores and primates, SMI-32 antibodies also serve as selective markers for visual neurons involved in motion detection and spatial vision [
16,
18].
A. cahirinus exhibits strong depth perception [
19,
20] and relies more on visual cues compared to their closest relatives, the gerbil species [
19,
21,
22]. Therefore, we expect to observe a well-developed population of SMI-32-immunopositive cells in the LGN of
A. cahirinus.
5. Conclusions
This study is the first to evaluate the organization and development of the LGN in A. cahirinus. Using several neurochemical markers, we identified the following functional subdivisions of the LGN in adult and newborn A. cahirinus: the “shell” and “core” parts of the LGNd, the inner and outer compartments of the LGNv, and the IGL. In adults and newborns, the “shell–core” distinction of the LGNd is visible only with CR staining. In adults, differentiating the LGNv into inner and outer parts was possible using various markers, including CB, CR, PV, GAD67, and SMI-32. In newborns, this division was achievable using CR and SMI-32 staining. In newborns, the LGNv is more developed compared to the LGNd, but in general, despite their early development, the visual system of newborn A. cahirinus is far from mature.
Author Contributions
Conceptualization, M.N.; methodology, M.N.; validation, M.N., A.M. and A.V.; formal analysis, M.N.; investigation, M.N., A.M. and A.V.; resources, M.N.; data curation, M.N.; writing–original draft preparation, M.N., A.M. and A.V.; writing–review and editing, M.N., A.M. and A.V.; visualization, M.N and A.V.; supervision, M.N.; project administration, M.N.; funding acquisition, M.N. All authors have read and agreed to the published version of the manuscript.
Figure 1.
The total scheme of the lateral geniculate nucleus (LGN) location in adult acomys. The region containing LGN at the Nissl staining slice is introduced into the scheme. Numericals are numbers of the frontal slices. The dorsal and ventral nuclei of the LGN (LGNd and LGNv) are labeled by green and pink. An intergeniculate leaflet (IGL) at all levels is located between the LGNd and LGNv. cp—cerebral pedunculi; eml—external medullary lamina; f—fornix; fr—fasciculus retroflexus; ic—internal capsule; MHb—medial habenula; ml—medial lemniscus; MR—mammillary region; mt—mammillary tract; ot—optic tract; pc—posterior commissure; pmt—principal mammillary tract; SC—superior colliculus; SN—substantia nigra; str—superior thalamic radiation. C-R—caudo-rostral direction.
Figure 1.
The total scheme of the lateral geniculate nucleus (LGN) location in adult acomys. The region containing LGN at the Nissl staining slice is introduced into the scheme. Numericals are numbers of the frontal slices. The dorsal and ventral nuclei of the LGN (LGNd and LGNv) are labeled by green and pink. An intergeniculate leaflet (IGL) at all levels is located between the LGNd and LGNv. cp—cerebral pedunculi; eml—external medullary lamina; f—fornix; fr—fasciculus retroflexus; ic—internal capsule; MHb—medial habenula; ml—medial lemniscus; MR—mammillary region; mt—mammillary tract; ot—optic tract; pc—posterior commissure; pmt—principal mammillary tract; SC—superior colliculus; SN—substantia nigra; str—superior thalamic radiation. C-R—caudo-rostral direction.
Figure 2.
The total scheme of the lateral geniculate nucleus (LGN) location in newborn acomys. The region containing LGN at the Nissl staining slice is introduced into the scheme. Numericals are numbers of the frontal slices. The dorsal and ventral nuclei of the LGN (LGNd and LGNv) are labeled by green and pink. An intergeniculate leaflet (IGL) at all levels is located between the LGNd and LGNv. cp—cerebral pedunculi; MHb—medial habenula; MR—mammillary region; SC—superior colliculus; SN—substantia nigra; C-R—caudo-rostral direction.
Figure 2.
The total scheme of the lateral geniculate nucleus (LGN) location in newborn acomys. The region containing LGN at the Nissl staining slice is introduced into the scheme. Numericals are numbers of the frontal slices. The dorsal and ventral nuclei of the LGN (LGNd and LGNv) are labeled by green and pink. An intergeniculate leaflet (IGL) at all levels is located between the LGNd and LGNv. cp—cerebral pedunculi; MHb—medial habenula; MR—mammillary region; SC—superior colliculus; SN—substantia nigra; C-R—caudo-rostral direction.
Figure 3.
An area of nuclei of the lateral geniculate complex: dorsal lateral geniculate nucleus (LGNd), ventral lateral geniculate nucleus (LGNv), and intergeniculate leaflet (IGL) (A) and the number of neurons stained for the calbindin (CB), calretinin (CR), parvalbumin (PV), glutamic acid decarboxylase isoform with molecular weights of 67 kDa (GAD67), and non-phosphorylated domains of the high-weighted neurofilaments (SMI-32) of adult (black) and newborn (gray) acomys (B-F). **** p < 0.0001, *** p < 0.001,** p < 0.01,* p < 0.05.
Figure 3.
An area of nuclei of the lateral geniculate complex: dorsal lateral geniculate nucleus (LGNd), ventral lateral geniculate nucleus (LGNv), and intergeniculate leaflet (IGL) (A) and the number of neurons stained for the calbindin (CB), calretinin (CR), parvalbumin (PV), glutamic acid decarboxylase isoform with molecular weights of 67 kDa (GAD67), and non-phosphorylated domains of the high-weighted neurofilaments (SMI-32) of adult (black) and newborn (gray) acomys (B-F). **** p < 0.0001, *** p < 0.001,** p < 0.01,* p < 0.05.
Figure 4.
Neurochemical staining of the lateral geniculate complex in adult (A) and newborn (B) acomyses using antibodies to calbindin (CB). LGNd and LGNv—dorsal and ventral lateral geniculate nucleus, IGL—intergeniculate leaflet; R, C, M, L—rostral, caudal, medial, and lateral directions. Calibration bar is 100 µm.
Figure 4.
Neurochemical staining of the lateral geniculate complex in adult (A) and newborn (B) acomyses using antibodies to calbindin (CB). LGNd and LGNv—dorsal and ventral lateral geniculate nucleus, IGL—intergeniculate leaflet; R, C, M, L—rostral, caudal, medial, and lateral directions. Calibration bar is 100 µm.
Figure 5.
Neurochemical staining of the lateral geniculate complex in adult (A) and newborn (B) acomyses using antibodies to calretinin (CR). LGNd and LGNv—dorsal and ventral lateral geniculate nucleus, IGL—intergeniculate leaflet; R, C, M, L—rostral, caudal, medial, and lateral directions. Calibration bar is 100 µm.
Figure 5.
Neurochemical staining of the lateral geniculate complex in adult (A) and newborn (B) acomyses using antibodies to calretinin (CR). LGNd and LGNv—dorsal and ventral lateral geniculate nucleus, IGL—intergeniculate leaflet; R, C, M, L—rostral, caudal, medial, and lateral directions. Calibration bar is 100 µm.
Figure 6.
Neurochemical staining of the lateral geniculate complex in adult (A) and newborn (B) acomyses using antibodies to parvalbumin (PV). LGNd and LGNv—dorsal and ventral lateral geniculate nucleus, IGL—intergeniculate leaflet; red dotted line—the assumed boundaries of the LGNv; R, C, M, L—rostral, caudal, medial, and lateral directions. Calibration bar is 100 µm.
Figure 6.
Neurochemical staining of the lateral geniculate complex in adult (A) and newborn (B) acomyses using antibodies to parvalbumin (PV). LGNd and LGNv—dorsal and ventral lateral geniculate nucleus, IGL—intergeniculate leaflet; red dotted line—the assumed boundaries of the LGNv; R, C, M, L—rostral, caudal, medial, and lateral directions. Calibration bar is 100 µm.
Figure 7.
Neurochemical staining of the lateral geniculate complex in adult (A) and newborn (B) acomyses using antibodies to GAD67 (CB). LGNd and LGNv—dorsal and ventral lateral geniculate nucleus, IGL—intergeniculate leaflet; R, C, M, L—rostral, caudal, medial, and lateral directions. Calibration bar is 100 µm.
Figure 7.
Neurochemical staining of the lateral geniculate complex in adult (A) and newborn (B) acomyses using antibodies to GAD67 (CB). LGNd and LGNv—dorsal and ventral lateral geniculate nucleus, IGL—intergeniculate leaflet; R, C, M, L—rostral, caudal, medial, and lateral directions. Calibration bar is 100 µm.
Figure 8.
Neurochemical staining of the lateral geniculate complex in adult (A) and newborn (B) acomyses, using antibodies to SMI-32. LGNd and LGNv—dorsal and ventral lateral geniculate nucleus, IGL—intergeniculate leaflet; R, C, M, L—rostral, caudal, medial, and lateral directions. Calibration bar is 100 µm.
Figure 8.
Neurochemical staining of the lateral geniculate complex in adult (A) and newborn (B) acomyses, using antibodies to SMI-32. LGNd and LGNv—dorsal and ventral lateral geniculate nucleus, IGL—intergeniculate leaflet; R, C, M, L—rostral, caudal, medial, and lateral directions. Calibration bar is 100 µm.
Figure 9.
A soma area (A) and the shape factor (B) of neurons stained for the calbindin (CB), calretinin (CR), parvalbumin (PV), glutamic acid decarboxylase isoform with molecular weights of 67 kDa (GAD67, GAD), and non-phosphorylated domains of the high-weighted neurofilaments (SMI-32) of the dorsal and ventral lateral geniculate nuclei (LGNd and LGNv) of adult (black) and newborn (gray) acomys. **** p < 0.0001, *** p < 0.001,** p < 0.01,* p < 0.05.
Figure 9.
A soma area (A) and the shape factor (B) of neurons stained for the calbindin (CB), calretinin (CR), parvalbumin (PV), glutamic acid decarboxylase isoform with molecular weights of 67 kDa (GAD67, GAD), and non-phosphorylated domains of the high-weighted neurofilaments (SMI-32) of the dorsal and ventral lateral geniculate nuclei (LGNd and LGNv) of adult (black) and newborn (gray) acomys. **** p < 0.0001, *** p < 0.001,** p < 0.01,* p < 0.05.
Table 1.
Soma size: soma area (µm2) and maximal and minimal diameters (µm), and the shape factor of immunopositive neurons located in the lateral geniculate nuclei: dorsal (LGNd) and ventral (LGNv), and in the intergeniculate leaflet (IGL), of adult and newborn acomyses. CB—calbindin, CR—calretinin, PV—parvalbumin, GAD67—glutamic acid decarboxylase, SMI-32—antibody to the non-phosphorylated heavy-chain neurofilaments. Data presented as mean ± SD, Mann–Whitney test was used.
Table 1.
Soma size: soma area (µm2) and maximal and minimal diameters (µm), and the shape factor of immunopositive neurons located in the lateral geniculate nuclei: dorsal (LGNd) and ventral (LGNv), and in the intergeniculate leaflet (IGL), of adult and newborn acomyses. CB—calbindin, CR—calretinin, PV—parvalbumin, GAD67—glutamic acid decarboxylase, SMI-32—antibody to the non-phosphorylated heavy-chain neurofilaments. Data presented as mean ± SD, Mann–Whitney test was used.
|
Adults |
Newborns |
|
LGNd |
LGNv |
IGL |
LGNd |
LGNv |
IGL |
Soma area, µm2 |
CB |
50.9 ± 5.3 |
50.5 ± 20.1 |
53.1 ± 11.0 |
56.6 ± 20.6 ns |
61.5 ± 6.9 * |
59.6 ± 7.6 ns |
CR |
51.7 ± 11.6 |
49.9 ± 12.6 |
– |
57.8 ± 8.7 ns |
48.6 ± 6.9 ns |
47.6 ± 4.9 ns |
PV |
– |
76.4 ± 29.7 |
– |
– |
61.8 ± 10.0 ns |
– |
GAD67 |
66.8 ± 16.9 |
80.6 ± 17.1 |
– |
57.5 ± 7.9 ns |
52.5 ± 14.2 ** |
– |
SMI-32 |
106.7 ± 23.8 |
115.1 ± 23.1 |
– |
83.7 ± 9.7 * |
120.8 ± 16.2 ns |
– |
Maximal diameter, µm |
CB |
11.8 ± 0.8 |
11.4 ± 2.0 |
12.6 ± 1.5 |
11.8 ± 2.4 ns |
12.3 ± 1.5 ns |
12.4 ± 0.9 ns |
CR |
11.6 ± 1.9 |
11.2 ± 1.6 |
11.9 ± 1.7 |
11.6 ± 1.0 ns |
10.6 ± 0.8 ns |
11.0 ± 0.6 ns |
PV |
– |
12.9 ± 2.3 |
– |
– |
11.2 ± 1.2 ns |
– |
GAD67 |
12.7 ± 1.1 |
13.7 ± 1.4 |
– |
12.0 ± 1.1 ns |
11.2 ± 1.6 * |
– |
SMI-32 |
14.7 ± 1.5 |
16.1 ± 1.7 |
– |
13.2 ± 0.7 ** |
16.8 ± 1.3 ns |
– |
Minimal diameter, µm |
CB |
7.3 ± 0.2 |
7.3 ± 1.7 |
6.9 ± 0.9 |
7.9 ± 1.8 ns |
8.1 ± 0.9 ns |
7.7 ± 0.7 * |
CR |
7.3 ± 0.9 |
7.2 ± 1.2 |
7.1 ± 1.2 |
8.0 ± 0.7 ns |
7.1 ± 0.5 ns |
6.7 ± 0.3 ns |
PV |
– |
8.3 ± 1.5 |
– |
– |
7.4 ± 0.6 ns |
– |
GAD67 |
7.7 ± 0.9 |
8.2 ± 1.3 |
– |
6.9 ± 0.5 * |
6.6 ± 0.9 * |
– |
SMI-32 |
9.9 ± 1.1 |
10.0 ± 0.9 |
– |
8.7 ± 0.6 * |
10.2 ± 0.7 ns |
– |
Shape factor, r.u. |
CB |
0.58 ± 0.05 |
0.61 ± 0.13 |
0.62 ± 0.05 |
0.56 ± 0.12 ns |
0.66 ± 0.14 ns |
0.65 ± 0.05 ns |
CR |
0.60 ± 0.10 |
0.68 ± 0.09 |
0.67 ± 0.03 |
0.68 ± 0.05 * |
0.74 ± 0.03 ** |
0.70 ± 0.02 * |
PV |
– |
0.77 ± 0.08 |
– |
– |
0.87 ± 0.04 ** |
– |
GAD67 |
0.75 ± 0.13 |
0.81 ± 0.03 |
– |
0.78 ± 0.06 ns |
0.79 ± 0.04 ns |
– |
SMI-32 |
0.86 ± 0.02 |
0.83 ± 0.02 |
– |
0.87 ± 0.03 ns |
0.82 ± 0.02 ns |
– |
Table 2.
Numerical density (cells/mm2) of immunopositive neurons located in the lateral geniculate nuclei: dorsal (LGNd) and ventral (LGNv), and in the intergeniculate leaflet (IGL) of adult and newborn acomyses. CB—calbindin, CR—calretinin, PV—parvalbumin, GAD67—isoform of glutamic acid decarboxylase, SMI-32—antibody to the non-phosphorylated heavy-chain neurofilaments. Data presented as mean ± SD, Mann–Whitney test was used.
Table 2.
Numerical density (cells/mm2) of immunopositive neurons located in the lateral geniculate nuclei: dorsal (LGNd) and ventral (LGNv), and in the intergeniculate leaflet (IGL) of adult and newborn acomyses. CB—calbindin, CR—calretinin, PV—parvalbumin, GAD67—isoform of glutamic acid decarboxylase, SMI-32—antibody to the non-phosphorylated heavy-chain neurofilaments. Data presented as mean ± SD, Mann–Whitney test was used.
|
Adults |
Newborns |
|
LGNd |
LGNv |
IGL |
LGNd |
LGNv |
IGL |
Number of neurons |
CB |
257 ± 166 |
12 ± 8 |
17 ± 5 |
3 ± 6 **** |
12 ± 4 ns
|
12 ± 4 * |
CR |
5 ± 2 |
31 ± 11 |
22 ± 8 |
37 ± 27 **** |
69 ± 23 *** |
35 ± 14 * |
PV |
– |
49 ± 12 |
– |
– |
4 ± 2 **** |
– |
GAD67 |
81 ± 17 |
9 ± 2 |
2 ± 2 |
36 ± 26 ** |
8 ± 3 ns
|
0.1 ± 0.2 ns
|
SMI-32 |
56 ± 17 |
29 ± 8 |
0.8 ± 0.9 |
82 ± 31 * |
76 ± 8 **** |
2 ± 2 * |
Cellular density |
CB |
517 ± 394 |
40 ± 28 |
– |
10 ± 17 **** |
43 ± 14 ns
|
– |
CR |
10 ± 5 |
99 ± 32 |
– |
124 ± 81 **** |
349 ± 109 **** |
– |
PV |
– |
241 ± 74 |
– |
– |
1 ± 2 **** |
– |
GAD67 |
154 ± 36 |
28 ± 11 |
– |
118 ± 85 ns
|
52 ± 16 ** |
– |
SMI-32 |
107 ± 36 |
147 ± 40 |
– |
330 ± 128 **** |
492 ± 90 **** |
– |
Table 3.
The list of antibodies.
Table 3.
The list of antibodies.
Antibody |
Host |
Clonality |
Dilution |
Manufacturer |
Lot |
RRID |
Calbindin |
Mouse |
Monoclonal |
1:10000 |
Sigma-Aldrich |
C9848 |
AB_476894 |
Calretinin |
Rabbit |
Polyclonal |
1:10000 |
Sigma-Aldrich |
AB5054 |
AB_2068506 |
Parvalbumin |
Rabbit |
Polyclonal |
1:5000 |
Abcam |
ab11427 |
AB_298032 |
GAD67 |
Mouse |
Monoclonal |
1:2000 |
Sigma-Aldrich |
MAB5406 |
AB_2278725 |
SMI-32 |
Mouse |
Monoclonal |
1:5000 |
BioLegend |
801701 |
AB_2564642 |